I guess that will be the case in the near future (<5 years). I believe streaming will be able to rival downloads after then.
Nope, it won't.
If you're into singleplayer stuff then the reliability of downloads is always going to be better than streaming. I mean, my internet is pretty shitty but even if you have good internet then bad weather could still mess up your connection and prevent you from playing games, or worse cut out a game you're currently playing before you can save it.
And if you're into multiplayer stuff then the increased lag of streaming is always going to put you at a disadvantage. Even if the streaming speed is amazing, you're still going to be slightly slower than somebody who has the game downloaded and if you're playing a competitive game why would you willingly disadvantage yourself?